What it is and what the ratings mean for fit
The Siemens 3VA1120-5GE42-0AA0 is a SENTRON molded case circuit breaker (MCCB) with a 20 A continuous rating across four poles, using a TM220 thermal-magnetic trip unit. That 20 A holds steady from 40 °C all the way up to 55 °C — it doesn't start derating until 60 °C, where it drops to 19 A, and it holds 19 A through 70 °C. This matters if you're stuffing this breaker into a warm cabinet or a motor control center where ambient heat is a given; you don't lose headroom until the panel is genuinely hot. The interrupting ratings tell the real story for line-side fault coordination: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at both 500 V and 690 V. That 187 kA at 240 V is a serious number — it means this breaker can sit on a high-capacity transformer secondary without needing a current-limiting fuse upstream. For a site electrical engineer working on selective coordination, that's the spec that decides whether the next breaker downstream clears before this one trips. Rated insulation voltage is 800 V, and the front face carries IP40 protection — fine for a dry indoor panel, but not for washdown areas. Power loss is 12 W maximum, which is modest for a 4-pole 20 A MCCB and won't cook adjacent components in a dense DIN-rail layout.
Panel integration and footprint
Dimensions are 130 mm high, 101.6 mm wide, and 70 mm deep. That 70 mm depth is shallow enough that it won't force a deeper enclosure than you'd use for a standard contactor or relay panel. The 101.6 mm width (4 inches) is the space you need to budget on the DIN rail — for a panel OEM wireman, that's four inches of rail you can't use for anything else per breaker. Plan your fill factor accordingly. The 4-pole configuration means this breaker switches all three phases plus the neutral. For a commissioning engineer, that's the right choice for a TN-S or TN-C-S system where you want the neutral isolated and protected alongside the line conductors. No undervoltage release, no trip indicator, no communication function — this is a straight line-protection device without accessories.
Lifecycle and sourcing reality
Operating temperature range is -25 °C to 70 °C, storage from -40 °C to 80 °C. That covers most indoor industrial environments short of a freezer or a foundry floor. For an MRO planner stocking a spare for a line-down scenario, this breaker will sit on a shelf in a non-conditioned warehouse without issue.
What it's for — deployment context
This is a molded case circuit breaker designed for line protection — meaning it sits at the distribution point in a panel, protecting the feeder cables and downstream loads from overloads and short circuits. It's not a motor-protective breaker with integrated overload class; it's a distribution MCCB. You'd find it in a main switchboard, a sub-distribution board, or as the incoming breaker in a motor control center bucket. For a field service tech swapping a failed unit, the TM220 trip unit is thermal-magnetic, so no external control power needed — it trips on its own internal mechanism.